A couple of days since my last post. Some minor progress, my first parts for my HK build have shipped.. I have ordered the grip housing, and all the parts for the fire-control-group (FCG). I started here, because I wanted to be able to play with it on my CETME, and I can assemble the lower, and install it on my CETME to play with it. So why the hell not? The biggest decisions I struggled with over the past couple of days was what type of HK 91 build I wanted.. I could go 16" barrel and go with an HK 93 forearm (not dissimlar to the PTR-KF models), or I could go old school and go with the original 17.7" barrel and traditional G3/91 forearm. Second major decision was did I want a telescoping (A3) style retractable stock, or the fixed A2 style. After many back and forth internal battles, and discussions with all of my firearm-minded friends, weighing the pros and cons of each configuration (thanks guys, you know who you are).. I have (I think) decided on the 17.7" old school original G3 design, with the wide, synthetic forarm, and A2 fixed synthetic stock. I have not yet decided on whether I will install the HK bipod, or not, but the wide forearm gives me the option. I also haven't decided on whether I will go with a claw-mount scope mount, or mount a picatinny style rail on top (which I already have, that I pulled off my CETME). I guess we'll cross that bridge when we get to it.
So, now onto locating a welder. See, my build is going to be from a flat (shown right, taken from http://www.hkparts.net), and so I will need to a.) bend the flat into the shape of the receiver, and b.) weld all the necessary accoutrement onto it (semi-auto shelf, rear sight base, receiver support). I could get a finished receiver, but then I am still left with welding irregardless (for the trunion and cocking tube welds), as well as having to go through an FFL. Plus, if I'm gonna weld, I might as well weld it all, baby!
Anyway, I completed my parts list, and all in all (with the necessary flat bending jig, I am looking long-term total cost at around $1,800 for the whole project), which, while more than a PTR-91, is much more fun too. Personal satisfaction of building my own HK, and being able to letter it as I see fit (which will be a separate post at a later time).
So onto baffles... well, suppressors in general. See, my cousin is going to be submitting a Form 1 and building his own suppressor. And he made the mistake of sending me some thoughts on his design.
The problem with that, is then I feel the need to provide my own opinion on it. So we delved into what became about a 3 hour discussion over IM about the merits of one baffle design over another (for those of you unfamiliar, a suppressor is fundamentally no different than a car's muffler, in fact, the design came FROM the muffler and is attributed to the same person). A set of baffles trap the expanding gas propelling the bullet, while allowing the bullet to pass through a hole in the center of the baffle. Many baffles line a silencer tube, and trap the gas, slowing the process of gas expansion, hence reducing the report of the gunshot. Now to be clear, it is NOT the mythical "phut" that you hear in movies or see on TV where a little black specops dude, is unleashing whispering death upon the unsuspecting terrorists where none are the wiser. The fact is, most suppressors reduce the sound of a gunshot by about 33 dB (an unsuppressed gunshot runs around 160-180 dB). You ever fire a gun without hearing protection? You ever fire a gun with one (I hope so!). Well the sound of a gunshot with the top of the line hearing protection is reduced by about 30 dB. So... a suppressed gun still sounds like a frickin' gun! It just makes one sound like a gun would sound when you've got earplugs in. Got it? Ok, good.. so.. anyway.. my cousin and I started thinking of ways to further slow the gas expansion down.. one way is through some basic fluid dynamics.. if you can produce a helical motion to the gas IN ADDITION to stopping it with the baffles, then you've created a further slowdown of gas expansion. See, the shortest path between two points is a straight line.. so, solution: make it NOT go in a straight line.. a helical motion in addition to baffling will force the gas out even slower, and further quieting the suppressor. Before you patent junkies get all excited, relax.. suppressor companies have already thought of this. http://www.thunderbeastarms.com has some of the world's most quietest silencers, and they use helical baffling systems to accomplish this. But my cousin wants to build his own.. so.. more power to him.. let's figure out how.. what we ultimately decided he should try is to have 3 vanes attached to the baffles, allowing the gas to tumble into the mouse holes (the 3 holes in addition to the bore hole at 120-degree angles around the perimeter of the baffle). The next baffle would offset these holes (and consequently the vanes) further disturbing the air and continuing the helical motion. It might work. Ultimately he's going to try it and see what happens.. if it doesn't then back to the drawing board. If it does, well, then great!
So this brings us back to the HK project... Where we stand now, is I need to find a TIG welder out there who can help... :) The acquisition of parts will be lengthy (another advantage of building is you can prolong and draw out the cost over MANY paychecks... which I need.. ). I will likely get the bolt carrier and receiver flat next.. so I can begin the bending/welding process. With cocking tube, handle, support and axle pin with spring, barrel and trunion to follow... with all of those, I can complete the upper receiver welding and fitting.. Oh, and the jig of course.. no bending without the jig... ;)
Pictures of the lower grip housing and FCG will be soon to follow with its subsequent assembly. Which brings me to mention.. Do you KNOW how hard it is to figure out exactly WHAT you can get away with in terms of BATFE? The full-auto FCGs are not restricted (unlike FCGs for an AR), but will NOT fit in a semi-auto receiver.. and grip housings come in a million flavors.. I figured I would play it safe and get a Safe/Fire only grip housing, and a semi-only FCG just to make sure that it all fits, and is all kosher with the BATFE. I might send them a letter and ask for clarification later and swap out some things later if I can legally, but for now.. I just want a working HK 91.
Until next time, cheers all!
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